1. Technical Field
The present invention relates to a piston for a hydraulic power assist rack and pinion steering system.
2. Description of the Prior Art
A known hydraulic power assist rack and pinion steering system for a vehicle comprises a rack movable to effect turning movement of the steerable wheels of the vehicle. A piston is mounted on the rack. A portion of the piston is received in one or more grooves in the rack to secure the piston to the rack. The piston forms part of a fluid motor for moving the rack in response to turning of the vehicle steering wheel.
The piston typically is formed by machining. In the machining process, a large amount of material is lost.
The present invention is a hydraulic power assist steering system for a vehicle having steerable wheels. The system comprises a housing and a rack movable in the housing to effect turning movement of the steerable wheels of the vehicle. The system also comprises a fluid motor for moving the rack. The fluid motor includes a piston fixedly connected to the rack and a pump. The piston has first and second opposite end faces against which hydraulic fluid is directed by the pump to effect movement of the piston, and thereby the rack, relative to the housing. The piston has a wall including a first end portion connected with the rack at a first axial location along the rack, a second end portion connected with the rack at a second axial location along the rack, and a central portion extending between and interconnecting the first and second end portions of the wall. The central portion of the wall has an outer peripheral groove for receiving a seal ring for engagement with the housing. The first end portion and the second end portion and the central portion of the piston define a cavity in the piston. The cavity has an annular configuration extending around the rack inside of the wall.